title: Photoinduced Ultrafast Dynamics of Ru(dcbpy)(2)(NCS)(2)-Sensitized Nanocrystalline TiO(2) Films: The Influence of Sample Preparation and Experimental Conditions.
abstract: In most of the previous ultrafast electron injection studies of Ru(dcbpy)2(NCS)2-sensitized nanocrystalline TiO2 films, experimental conditions and sample preparation have been different from study to study and no studies of how the differences affect the observed dynamics have been reported. In the present paper, we have investigated the influence of such modifications. Pump photon density, environment of the sensitized film (solvent and air), and parameters of the film preparation (crystallinity and quality of the film) were varied in a systematic way and the obtained dynamics were compared to that of a well-defined reference sample: Ru(dcbpy)2(NCS)2-TiO2 in acetonitrile. In some cases, the induced changes in the dynamics were uncorrelated to the electron injection process. High pump photon density (not in the linear response region) and exposure of the sensitized film to air altered the picosecond-time-scale kinetics considerably, and the changes were attributed mostly to degradation of the dye. In other cases, changes in the measured kinetics were related to the electron injection processes: reducing the firing temperature of the nanocrystalline film or making the film via electron beam evaporation (EBE) resulted in a decrease of the overall crystallinity of the film, and the electron injection slowed. In the sensitized EBE films, in addition to an increased contribution of triplet excited-state electron injection, a new electron transfer (ET) process with a time constant of 200 fs was observed.
authors.affiliation: Department of Chemistry, University of Jyväskylä, P.O. Box 35, FIN-40014 Jyväskylä, Finland, Department of Chemical Physics, Lund University, P.O. Box 124, SE-22100 Lund, Sweden, Laboratory of Physical Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland, Department of Materials Chemistry, Lund University, P.O. Box 124, SE-22100, Lund, Sweden, and VTT Electronics, P.O. Box 1100, FIN-90571 Oulu, Finland.
authors.forename: Jani
authors.initials: J
authors.lastname: Kallioinen
authors.forename: Gabor
authors.initials: G
authors.lastname: Benkö
authors.forename: Pasi
authors.initials: P
authors.lastname: Myllyperkiö
authors.forename: Leonid
authors.initials: L
authors.lastname: Khriachtchev
authors.forename: Björn
authors.initials: B
authors.lastname: Skårman
authors.forename: Reine
authors.initials: R
authors.lastname: Wallenberg
authors.forename: Markus
authors.initials: M
authors.lastname: Tuomikoski
authors.forename: Jouko
authors.initials: J
authors.lastname: Korppi-Tommola
authors.forename: Villy
authors.initials: V
authors.lastname: Sundström
authors.forename: Arkady P
authors.initials: AP
authors.lastname: Yartsev